1. Field of the Invention
The present invention relates to a filament winding method, a filament winding apparatus and a tank.
2. Description of the Related Art
A fuel cell power system is mounted, for example, in a vehicle or the like, and a gas tank is used as a source of fuel gas supply.
This type of gas tank is made by a filament winding method (hereinafter referred to as “FW method”). The FW method includes a process of forming a fiber reinforced plastics (FRP) layer around a substantially ellipse liner (inner container). In this process, fibers impregnated with thermosetting resins are usually wound around the liner.
In the FW method, hoop winding and helical winding are both performed. In the hoop winding, the FRPs are wound around a tank perpendicular to the tank axis. In the helical winding, the FRPs are wound around the tank obliquely to the tank axis. The hoop winding and the helical winding are alternately performed at predetermined times, and fiber reinforced plastics layers are formed around a circumference surface of the gas tank.
The helical winding of the FW method includes a multi-yarn feeding method, in which a large number of fibers are simultaneously wound around a liner from multiple directions. This multi-yarn feeding method significantly reduces the time taken to wind fibers around a liner.
In the multi-yarn feeding method, a helical winding head is used. The helical winding head feeds a large number of fibers to a gas tank from a plurality of positions on a concentric circle around the gas tank. While the rotating gas tank relatively reciprocates in the tank axial direction to the helical winding head, a plurality of fibers are fed from the helical winding head to the gas tank. In this way, the helical winding is performed on the gas tank.
Meanwhile, at the end of the helical winding, trailing ends of a large number of fibers need to be fastened to the gas tank. As a method for fastening the trailing ends, the following methods have already been proposed: a method for twisting the trailing ends of fibers around mouthpieces positioned at both ends of a gas tank or a method for securing the trailing ends of fibers with a resin clip to the gas tank.